1. Field of the Invention
The present invention relates to a movable valve train for an internal combustion engine, and to an engine and a motorcycle incorporating the same. More particularly, the present invention relates to a valve train having a link mechanism for swinging a valve-operating cam, and a drive mechanism operable to turn a holder member for varying positions of the link mechanism, and to an engine and a motorcycle including the same.
2. Description of the Background Art
There is known a movable valve train for an internal combustion engine. The movable valve train includes a drive cam rotated integrally with a camshaft supported by a cylinder head, and a valve-operating cam swingably supported by the camshaft to operate, i.e., to open and close engine valves. In addition, the movable valve train includes a link mechanism supported swingably around the camshaft for transmitting a valve driving force of the drive cam to the valve-operating cam for swing, a holder member connected to the link mechanism and turnable around the camshaft, and a drive mechanism for turning the holder member for varying positions of the support member of the link mechanism. The valve train configured as above can vary operating characteristics of the engine valve depending on the swing position of the swung link mechanism.
An example of such known movable valve train for an internal combustion engine is disclosed in the Japanese Patent Laid-open No. 2008-208800.
Incidentally, the movable valve train as described above is desired to connect the holder member connected to the link mechanism with the drive mechanism by a simple configuration and by using small number of parts.
In view of the above situations, the present invention has been made. Accordingly, one of the objects of the present invention is to provide a movable valve train for an internal combustion engine that can connect a holder member connected to a link mechanism with a drive mechanism by means of a small-sized lightweight configuration having a small number of parts.